Enable usage of experimental inet_backend option for TCP listeners

src/ranch_acceptors_sup.erl

@@ -59,12 +59,7 @@ start_listen_sockets(Ref, NumListenSockets, Transport, TransOpts0, Logger) when
 			[];
 		{_, Port} ->
 			SocketOpts = maps:get(socket_opts, TransOpts0, []),
-			SocketOpts1 = case lists:keyfind(port, 1, SocketOpts) of
-				{port, Port} ->
-					SocketOpts;
-				_ ->
-					[{port, Port}|lists:keydelete(port, 1, SocketOpts)]
-			end,
+			SocketOpts1 = lists:keystore(port, 1, SocketOpts, {port, Port}),
 			TransOpts1 = TransOpts0#{socket_opts => SocketOpts1},
 			[{N, start_listen_socket(Ref, Transport, TransOpts1, Logger)}
 				|| N <- lists:seq(2, NumListenSockets)]

src/ranch_tcp.erl

@@ -89,16 +89,24 @@ messages() -> {tcp, tcp_closed, tcp_error, tcp_passive}.
 listen(TransOpts) ->
 	ok = cleanup(TransOpts),
 	Logger = maps:get(logger, TransOpts, logger),
-	SocketOpts0 = maps:get(socket_opts, TransOpts, []),
+	SocketOpts = maps:get(socket_opts, TransOpts, []),
+	%% We set the port to 0 because it is given in the Opts directly.
+	%% The port in the options takes precedence over the one in the
+	%% first argument.
+	gen_tcp:listen(0, prepare_socket_opts(SocketOpts, Logger)).
+
+prepare_socket_opts([Backend = {inet_backend, _}|SocketOpts], Logger) ->
+	%% In OTP/23, the inet_backend option may be used to activate the
+	%% experimental socket backend for inet/gen_tcp. If present, it must
+	%% be the first option in the list.
+	[Backend|prepare_socket_opts(SocketOpts, Logger)];
+prepare_socket_opts(SocketOpts0, Logger) ->
 	SocketOpts1 = ranch:set_option_default(SocketOpts0, backlog, 1024),
 	SocketOpts2 = ranch:set_option_default(SocketOpts1, nodelay, true),
 	SocketOpts3 = ranch:set_option_default(SocketOpts2, send_timeout, 30000),
 	SocketOpts4 = ranch:set_option_default(SocketOpts3, send_timeout_close, true),
-	%% We set the port to 0 because it is given in the Opts directly.
-	%% The port in the options takes precedence over the one in the
-	%% first argument.
-	gen_tcp:listen(0, ranch:filter_options(SocketOpts4, disallowed_listen_options(),
-		[binary, {active, false}, {packet, raw}, {reuseaddr, true}], Logger)).
+	ranch:filter_options(SocketOpts4, disallowed_listen_options(),
+		[binary, {active, false}, {packet, raw}, {reuseaddr, true}], Logger).
 
 %% 'binary' and 'list' are disallowed but they are handled
 %% specifically as they do not have 2-tuple equivalents.

test/acceptor_SUITE.erl

@@ -34,6 +34,7 @@ groups() ->
 		tcp_active_n_echo,
 		tcp_echo,
 		tcp_local_echo,
+		tcp_socket_echo,
 		tcp_graceful,
 		tcp_inherit_options,
 		tcp_max_connections,
@@ -916,6 +917,33 @@ do_tcp_local_echo() ->
 		file:delete(SockFile)
 	end.
 
+tcp_socket_echo(_) ->
+	%% The socket backend for inet/gen_tcp was introduced as an experimental
+	%% feature in OTP/23. erlang:atom_to_binary/1 first appears in this
+	%% release.
+	case erlang:function_exported(erlang, atom_to_binary, 1) of
+		true ->
+			do_tcp_socket_echo();
+		false ->
+			{skip, "No socket backend support."}
+	end.
+
+do_tcp_socket_echo() ->
+	doc("Ensure that using the socket backend works with TCP transport."),
+	Name = name(),
+	{ok, _} = ranch:start_listener(Name,
+		ranch_tcp, #{socket_opts => [{inet_backend, socket}]},
+		echo_protocol, []),
+	Port = ranch:get_port(Name),
+	{ok, Socket} = gen_tcp:connect("localhost", Port, [binary, {active, false}, {packet, raw}]),
+	ok = gen_tcp:send(Socket, <<"TCP Ranch is working!">>),
+	{ok, <<"TCP Ranch is working!">>} = gen_tcp:recv(Socket, 21, 1000),
+	ok = ranch:stop_listener(Name),
+	{error, closed} = gen_tcp:recv(Socket, 0, 1000),
+	%% Make sure the listener stopped.
+	{'EXIT', _} = begin catch ranch:get_port(Name) end,
+	ok.
+
 tcp_graceful(_) ->
 	doc("Ensure suspending and resuming of listeners does not kill active connections."),
 	Name = name(),